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The protein kinase LKB1 negatively regulates bone morphogenetic protein receptor signaling.

ABSTRACT: The protein kinase LKB1 regulates cell metabolism and growth and is implicated in intestinal and lung cancer. Bone morphogenetic protein (BMP) signaling regulates cell differentiation during development and tissue homeostasis. We demonstrate that LKB1 physically interacts with BMP type I receptors and requires Smad7 to promote downregulation of the receptor. Accordingly, LKB1 suppresses BMP-induced osteoblast differentiation and affects BMP signaling in Drosophila wing longitudinal vein morphogenesis. LKB1 protein expression and Smad1 phosphorylation analysis in a cohort of non-small cell lung cancer patients demonstrated a negative correlation predominantly in a subset enriched in adenocarcinomas. Lung cancer patient data analysis indicated strong correlation between LKB1 loss-of-function mutations and high BMP2 expression, and these two events further correlated with expression of a gene subset functionally linked to apoptosis and migration. This new mechanism of BMP receptor regulation by LKB1 has ramifications in physiological organogenesis and disease.

SUBMITTER: Raja E

PROVIDER: S-EPMC4811448 | biostudies-literature | 2016 Jan

REPOSITORIES: biostudies-literature

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The protein kinase LKB1 negatively regulates bone morphogenetic protein receptor signaling.

Raja Erna E Tzavlaki Kalliopi K Vuilleumier Robin R Edlund Karolina K Kahata Kaoru K Zieba Agata A Morén Anita A Watanabe Yukihide Y Voytyuk Iryna I Botling Johan J Söderberg Ola O Micke Patrick P Pyrowolakis George G Heldin Carl-Henrik CH Moustakas Aristidis A

Oncotarget 20160101 2

The protein kinase LKB1 regulates cell metabolism and growth and is implicated in intestinal and lung cancer. Bone morphogenetic protein (BMP) signaling regulates cell differentiation during development and tissue homeostasis. We demonstrate that LKB1 physically interacts with BMP type I receptors and requires Smad7 to promote downregulation of the receptor. Accordingly, LKB1 suppresses BMP-induced osteoblast differentiation and affects BMP signaling in Drosophila wing longitudinal vein morphoge ...[more]

PMID: 26701726

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Project description:NF?B signaling is of paramount importance in the regulation of apoptosis, proliferation, and inflammatory responses during human development and homeostasis, as well as in many human cancers. Receptor Tyrosine Kinases (RTKs), including the Fibroblast Growth Factor Receptors (FGFRs) are also important in development and disease. However, a direct relationship between growth factor signaling pathways and NF?B activation has not been previously described, although FGFs have been known to antagonize TNF?-induced apoptosis.Here, we demonstrate an interaction between FGFR4 and IKK? (Inhibitor of NF?B Kinase ? subunit), an essential component in the NF?B pathway. This novel interaction was identified utilizing a yeast two-hybrid screen [1] and confirmed by coimmunoprecipitation and mass spectrometry analysis. We demonstrate tyrosine phosphorylation of IKK? in the presence of activated FGFR4, but not kinase-dead FGFR4. Following stimulation by TNF? (Tumor Necrosis Factor ?) to activate NF?B pathways, FGFR4 activation results in significant inhibition of NF?B signaling as measured by decreased nuclear NF?B localization, by reduced NF?B transcriptional activation in electophoretic mobility shift assays, and by inhibition of IKK? kinase activity towards the substrate GST-I?B? in in vitro assays. FGF19 stimulation of endogenous FGFR4 in TNF?-treated DU145 prostate cancer cells also leads to a decrease in IKK? activity, concomitant reduction in NF?B nuclear localization, and reduced apoptosis. Microarray analysis demonstrates that FGF19 + TNF? treatment of DU145 cells, in comparison with TNF? alone, favors proliferative genes while downregulating genes involved in apoptotic responses and NF?B signaling.These results identify a compelling link between FGFR4 signaling and the NF?B pathway, and reveal that FGFR4 activation leads to a negative effect on NF?B signaling including an inhibitory effect on proapoptotic signaling. We anticipate that this interaction between an RTK and a component of NF?B signaling will not be limited to FGFR4 alone.

Project description:BackgroundThe endoplasmic reticulum (ER) contacts endosomes in all parts of a motor neuron, including the axon and presynaptic terminal, to move structural proteins, proteins that send signals, and lipids over long distances. Atlastin (Atl), a large GTPase, is required for membrane fusion and the structural dynamics of the ER tubules. Atl mutations are the second most common cause of Hereditary Spastic Paraplegia (HSP), which causes spasticity in both sexes' lower extremities. Through an unknown mechanism, Atl mutations stimulate the BMP (bone morphogenetic protein) pathway in vertebrates and Drosophila. Synaptic defects are caused by atl mutations, which affect the abundance and distribution of synaptic vesicles (SV) in the bouton. We hypothesize that BMP signaling, does not cause Atl-dependent SV abnormalities in Drosophila.ResultsWe show that atl knockdown in motor neurons (Atl-KD) increases synaptic and satellite boutons in the same way that constitutively activating the BMP-receptor Tkv (thick veins) (Tkv-CA) increases the bouton number. The SV proteins Cysteine string protein (CSP) and glutamate vesicular transporter are reduced in Atl-KD and Tkv-CA larvae. Reducing the activity of the BMP receptor Wishful thinking (wit) can rescue both phenotypes. Unlike Tkv-CA larvae, Atl-KD larvae display altered activity-dependent distributions of CSP staining. Furthermore, Atl-KD larvae display an increased FM 1-43 unload than Control and Tkv-CA larvae. As decreasing wit function does not reduce the phenotype, our hypothesis that BMP signaling is not involved is supported. We also found that Rab11/CSP colocalization increased in Atl-KD larvae, which supports the concept that late recycling endosomes regulate SV movements.ConclusionsOur findings reveal that Atl modulates neurotransmitter release in motor neurons via SV distribution independently of BMP signaling, which could explain the observed SV accumulation and synaptic dysfunction. Our data suggest that Atl is involved in membrane traffic as well as formation and/or recycling of the late endosome.

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The protein kinase LKB1 negatively regulates bone morphogenetic protein receptor signaling.

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The protein kinase LKB1 negatively regulates bone morphogenetic protein receptor signaling.

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